1. Field of the Invention
The present invention relates to a button cover holding mechanism of a portable telephone, and more particularly to a button cover holding mechanism for opening and closing a button cover which is engaged with a body of the portable telephone.
A button cover holding mechanism of a portable telephone according to the present invention is based on Korean Application No. 21323/95 which is incorporated herein by reference.
2. Description of the Related Art
In the prior art in which portable telephones include a body with dial buttons and function buttons, it has been a disadvantage in that some buttons are unintentionally pressed, thereby causing an erroneous operation of the portable telephone. To prevent such erroneous operation, the body is provided with the button cover so that the button surface is protected from an unintentional external force. Many technologies for the button cover holding mechanism of the portable telephone have been developed, such as described in U.S. Pat. No. 5,257,310.
For example, in the prior art, with reference to FIGS. 1 and 2, a cylindrical bush 32 is inserted into a circular hole 20 of a cover mounting projection 18 of a case 2, and a pipe shaft 30 having a wave cam 40 formed at its inner end is fitted into the cylindrical bush 32. The cylindrical bush 32 is fixed to a hinge portion 34 of the cover 14, and pins 36 are inserted at both sides for preventing rotation of the pipe shaft 30, the cylindrical bush 32 and the hinge portion 34 of the cover 14. Also, two L-shaped bent ends 38a of a spring 38 fixed to the case 2 are fitted into the pipe shaft 30.
If the L-shaped bent ends 38a of the spring 38 are positioned at trough portions 40b and 40d of the wave cam 40 of the pipe shaft 30 of FIG. 2, no elastic force acts on the pipe shaft 30 due to a non-deformation of the spring 38. However, if the L-shaped bent ends 38a are positioned at crest portions 40a and 40c of the wave cam 40 of the pipe shaft 30, elastic force acts on the pipe shaft 30 due to a deformation of the spring 38.
If the end 38a of the spring 38 is positioned at the trough portion 40b of the wave cam 40 of the pipe shaft 30, the cover 14 is maintained in a stable configuration, in which the cover 14 is maintained in a plane parallel to a plane D as shown in FIG. 2, allowing it to remain opened when inclined by 145.degree. with respect to the case 2 parallel to a plane C.
On the other hand, if the end 38a of the spring 38 is positioned at the plane C, the end 38a is in contact with a portion of the wave cam 40 at a position between the crest portion 40a and the trough portion 40d. Accordingly, the elastic force of the spring 38 acts on the pipe shaft 30 in a direction for closing the cover 14, so that the cover 14 is maintained in a closed configuration.
However, in the prior art button cover holding mechanisms of the portable telephone have had disadvantages in which it is difficult to assemble the hinge portion 34, the cylindrical bush 32 and the pipe shaft 30 with respect to one another since the pin 36 should be force-fitted at both sides so as to prevent rotation of the hinge portion 34, the cylindrical bush 32 and the pipe shaft 30 of the cover 14, and also in which an appearance of the portable telephone as a high quality product is compromised since the pin 36 appears exposed.
Also, there have been disadvantages in that the pipe shaft 30 should be manufactured as a material identical with the material of the spring 38 so as to reduce an abrasion of the pipe shaft 30 caused by the friction of the ends 38a of the spring 38 which are in contact with the wave cam 40 of the pipe shaft 30. Accordingly, the pipe shaft 30 should be manufactured by a diecast or a mechanical processing, which increases the product cost as well as the product weight, but which causes the component holding volume of the case 2 to be reduced due to the space occupied by the spring 38, which thus prevents miniaturization of the product.
Moreover, there have been disadvantages in that, when the cover 14 is in a closed condition, an angle range for closing the cover 14 is relatively large (e.g. it may be more than 72.5.degree.) over which the ends 38a of the spring 38 are moved from the trough portion 40d to the crest portion 40a of the wave cam 40 of the pipe shaft 30, which causes inconvenience to the user and which causes the ends 38a of the spring 38 to be in contact with only one portion of the wave cam 40 of the pipe shaft 30, thereby reducing the force for rotating the cover 14.